Detection and enumeration of reticulocyte cells has provided extensive challenge to designers and manufacturers of automated hematology instruments. Reticulocytes are precursors to red blood cells, and hence the term reticulocyte embraces the evolution and development of the cell whereby the red blood cell is generated. Hence, a cell which is clearly a red cell precursor today will be a red blood cell in a few days more, and will of course mature during the interim. It is, therefore, quite difficult to define objective criteria whereby reticulocytes may be effectively discriminated from red cells. Correspondingly, criteria which have heretofore been developed tend to involve quite subjective interpretations, whereby even the most meticulous manual counts, for example utilizing microscopic optical scanning techniques, will yield results of moderate to extensive disparity.
It is an object of the present invention to provide an automated, effective, highly repeatable approach to discrimination of reticulocytes from red blood cells.
An approach to automated hematology which is increasingly finding acceptance as the preferred approach is one often designated as optical flow cytometry. Such systems employ a hydrodynamically focused channel through which blood cells are passed extremely rapidly, one at a time. The constriction of the channel is illuminated by precisely focused light, for example coherent radiation from a laser. Much can be determined by analysis of light scattered by the cells, and if the blood sample has been treated with specific staining agents, still more can be determined by suitable analysis of fluorescent light stimulated from a stained cell or other fluorescent material passing through the focusing zone.
It is an object of the present invention to utilize the principles of optical flow cytometry automatically and repeatably to identify and enumerate platelets, reticulocytes, and red blood cells in a whole blood sample.